Atmosphere control for cargo storage spaces

1. A controlled atmosphere system for a cargo storage space, the system comprising:

a separation area for receiving atmospheric gas from the cargo storage space;

a gas moving device arranged to move atmospheric gas from the cargo storage space into the separation area to thereby increase a pressure within the separation area; and

a molecular sieve including a membrane which is permeable to selected molecules, the molecular sieve being arranged in communication with the separation area such that, when the separation area is at an overpressure, the selected molecules are continuously vented out of the separation area through the molecular sieve at a removal rate that is substantially proportional to a pressure gradient across the molecular sieve.

2. A controlled atmosphere system as claimed in claim 1 , wherein the separation area is separated from the cargo storage area by a barrier.

3. A controlled atmosphere system as claimed in claim 2 , wherein the barrier is a housing.

4. A controlled atmosphere system as claimed in claim 1 , wherein the molecular sieve defines a boundary of the separation area.

5. A controlled atmosphere system as claimed in claim 1 , wherein the separation area further comprises a return outlet for flowing recirculated gas from the separation area to the cargo storage space, the return outlet provided with a throttling valve for throttling flow from the separation area to the cargo storage space.

6. A controlled atmosphere system as claimed in claim 5 , wherein the throttling valve is controllable to thereby alter the pressure within the separation area.

7. A controlled atmosphere system as claimed in claim 1 , wherein the gas moving device is controllable to thereby alter the pressure within the separation area.

8. A controlled atmosphere system as claimed in claim 1 , wherein the selected molecules vented through the molecular sieve are vented into an ambient environment.

9. A controlled atmosphere system as claimed in claim 1 , wherein a venting area is arranged on an opposite side of the molecular sieve to the separation area such that the selected molecules are vented out of the separation area into the venting area through the molecular sieve.

10. A controlled atmosphere system as claimed in claim 9 , wherein the venting area is an enclosed area having a venting outlet.

11. A controlled atmosphere system as claimed in claim 10 , wherein the molecular sieve is arranged within a sieve chamber such that the separation area is a portion of the sieve chamber on a first side of the molecular sieve, and the venting area is a portion of the sieve chamber on a second side of the molecular sieve.

12. A controlled atmosphere system as claimed in claim 1 , wherein the separation area is arranged within the cargo storage space.

13. A controlled atmosphere system as claimed in claim 9 , wherein the venting area is arranged outside the cargo storage space or within the cargo storage space.

14. A controlled atmosphere system as claimed in claim 9 , wherein the separation area and the venting area are arranged outside the cargo storage space.

15. A controlled atmosphere system as claimed in claim 1 , wherein the selected molecules comprise carbon dioxide molecules.

16. A controlled atmosphere system as claimed in claim 1 , wherein the molecular sieve inhibits the passage of oxygen and/or nitrogen molecules therethrough.

17. A controlled atmosphere system as claimed in claim 1 , further comprising a sensor for detecting one or more characteristics of the atmospheric gas in the cargo storage space.

18. A controlled atmosphere system as claimed in claim 17 , further comprising a controller for adjusting the overpressure in the separation area by adjusting the operation of the gas moving device and/or the throttling valve based upon the detected characteristic.

19. A controlled atmosphere system as claimed in claim 17 , wherein the detected characteristic is a carbon dioxide concentration in the atmospheric gas in the cargo storage space.

20. A cargo storage unit comprising a cargo storage space and a controlled atmosphere system in accordance with claim 1 , the gas moving device being arranged to receive atmospheric gas from the cargo storage space for moving into the separation area.

21. A cargo storage unit as claimed in claim 20 , further comprising a refrigeration unit for cooling the cargo storage space.

22. A cargo storage unit as claimed in claim 21 , wherein the controlled atmosphere system is in communication with a condenser section of the refrigeration unit such that the selected molecules sieved from the separation area by the molecular sieve can be vented to the condenser section.

23. A cargo storage unit as claimed in claim 20 , wherein the cargo storage unit is an intermodal freight container.

24. A method of controlling the atmosphere of a cargo storage space comprising:

providing a separation area for receiving atmospheric gas from the cargo storage space;

providing a molecular sieve in communication with the separation area, the molecular sieve including a membrane which is permeated by selected molecules; and

creating an overpressure in the separation area by moving atmospheric gas from the cargo storage space into the separation area to thereby continuously vent the selected molecules from the separation area through the molecular sieve at a removal rate that is substantially proportional to a pressure gradient across the molecular sieve.